Using butyl titanate and absolute ethanol as raw materials, TiO₂ was prepared by a hydrothermal method with different hydrothermal times, and the influences of hydrothermal time on the structure and photocatalytic performance of TiO₂ were investigated. The obtained samples were characterized by XRD, SEM, TEM, BET, PL and DRS, separately. The results show that TiO₂ forms anatase when the hydrothermal time is 12 h, forms a mixed crystal composed of anatase and rutile when the hydrothermal time is 24 h, and forms rutile when the hydrothermal time is 36 h. With the extension of hydrothermal time, anatase gradually transforms into rutile and the surface area decreases. Although TiO₂-24 h and TiO₂-36 h show lower photoinduced charge recombination and higher light source utilization, TiO₂-12 h exhibits the highest photocatalytic activity owing to its largest surface area (145.3 m²/g). The degradation degree of rhodamine B and tetracycline hydrochloride reach 99.6% and 90.0% after 45 min.

Pure and Ag/AgCl-modified titania powders with anatase/rutile/brookite three-phase mixed structure were prepared by one-step hydrothermal method. The effects of Ag/Ti atomic percentages on the structure and photocatalytic performance of TiO₂ were investigated. The results showed that pure TiO₂ consisted of three phases, anatase, rutile, and brookite, and that Ag addition promoted the transformation from anatase to rutile. When the molar ratio of Ag/Ti reached 4%, the AgCl phase appeared. The addition of Ag had little effect on the optical absorption of TiO₂; however, it did favor the separation of photogenerated electrons and holes. The results of photocatalytic experiments showed that after Ag addition, the degradation degree of rhodamine B (RhB) was enhanced. When the molar ratio of Ag/Ti was 4%, Ag/AgCl-modified TiO₂ exhibited the highest activity, and the first-order reaction rate constant was 1.67 times higher than that of pure TiO₂.

In this study, pure CeO₂ and oxygen-vacancy-enriched SnO₂-CeO₂ composite materials were prepared using the sol–gel method, and their microstructures and photocatalytic properties were investigated. The results indicate that SnO₂ coupling promotes the separation and transfer of photogenerated electrons and holes and suppresses their recombination. The 50% SnO₂-CeO₂ composite material exhibited a decreased specific surface area compared to pure CeO₂ but significantly increased oxygen vacancy content, demonstrating the highest photogenerated charge separation efficiency and the best photocatalytic performance. After 120 min of illumination, the degradation degree of MB by the 50% SnO₂-CeO₂ composite material increased from 28.8% for pure CeO₂ to 90.8%, and the first-order reaction rate constant increased from 0.002 min⁻¹ to 0.019 min⁻¹.

Pure and Sn/Ni co–doped TiO₂ nanomaterials with anatase/rutile mixed crystal were prepared and characterized. The results show that pure TiO₂ is a mixed crystal structure composed of a large amount of anatase and a small amount of rutile. Sn doping promotes the phase transformation from anatase to rutile, while Ni doping inhibits the transformation. Both single doping and co–doping are beneficial to the inhibition of photoinduced charge recombination. Sn doping shows the best inhibitory effect on photogenerated charge recombination, and increases the utilization of visible light, displaying the highest photocatalytic activity. The decolorization degree of methylene blue (MB) by Sn–TiO₂ is 79.5% after 150 min. The reaction rate constant of Sn–TiO₂ is 0.01022 min⁻¹, which is 5.6 times higher than pure TiO₂ (0.00181 min^–1).

The anatase/rutile mixed crystal TiO₂ was prepared and modified with Ag decoration and SnO₂ coupling to construct a Ag@SnO₂/anatase/rutile composite photocatalytic material. The crystal structure, morphology, element valence, optical properties and surface area were characterized, and the effects of Ag decoration and SnO₂ coupling on the structure and photocatalytic properties of TiO₂ were studied. Ag decoration and SnO₂ coupling are beneficial to reduce the recombination of photogenerated electrons and holes. When the two modification are combined, a synergistic effect is produced in suppressing the photogenerated charge recombination, making Ag@SnO₂/TiO₂ exhibits the highest quantum utilization. After 30 min of illumination, the degradation degree of tetracycline hydrochloride (TC) by pure TiO₂ increased from 63.3% to 83.1% with Ag@SnO₂/TiO₂.

Gel precursors were formed by reacting bismuth nitrate pentahydrate, acetic acid, sodium metavanadate, and NaOH. pH was adjusted using NaOH solution followed by calcination to obtain bismuth vanadate (BiVO₄) photocatalysts. During synthesis, pH directly influenced the formation and structure of the gel network. Therefore, the effects of pH on the microstructure and photocatalytic activity of BiVO₄ were investigated. At pH 3, the sample consisted of microspheres formed by tightly packed small particles. At pH 5, the microspheres transformed into aggregated flakes. Photocatalytic performance was evaluated through methylene blue (MB) degradation, revealing the sample prepared at pH 7 (7-BVO) demonstrated the highest efficiency. The electronic band structure, bandgap, and band edge positions of 7-BVO were probed by density functional theory (DFT) and UV-vis absorption spectra. Furthermore, photoluminescence spectroscopy, electrochemical measurements, active species trapping experiments and liquid chromatography mass spectrometry technique collectively revealed the possible mechanistic pathways for MB photodegradation by 7-BVO.